Multiple-position rotary stepping switch having an obliquely oriented contact bridge



March 23, 1965 w. E. LUDWIG 3,175,052

MULTIPLE-POSITION ROTARY STEPPING SWITCH HAVING AN OBLIQUELY ORIENTED CONTACT BRIDGE Filed July 20, 1961 5' 1 PH/bR ART Fig-2 United States Patent Claims. (31. 200-11) The present invention relates to a switch, and, more particularly, to a rotary stepping switch equipped with one or more switching plates provided with printed circuits.

In recent times, printed circuits have come into increasingly frequent use in the electrical engineering arts; such printed circuits have, inter alia, been incorporated in switches used for various types of electrical equip ment. This is particularly so in electrical measuring devices which have to be built very small, in which case the switches have planar contact arrangements or switching plates provided with printed circuitry. In so-called multiple-purpose meters, such as are used in the electrical measurement arts for measuring currents, voltages and sometimes also resistances, a range selector is used which is fashioned as a rotary stepping switch. The current measuring ranges are distributed over approximately 180, and the voltage measurement ranges over the remaining 180. For design and engineering reasons, the switching of the current and voltage ranges is carried out in two planes of the rotary switch, i.e., separate switching plates are provided. Each plate will then have its 360 distributed in such a manner that the stepping contacts for changing the ranges are accommodated between the O and 180 positions, while a continuous, arcuate contact is arranged between the 180 and 360 positions. With instruments having three or four terminals it is customary not to interrupt the current circuit within the instruments when voltage measurements are being carried out. The switch thus has to provide a short circuit throughout approximately 180 or must close the electrical path of the individual contacts.

FIGURE 1 shows a typical contact arrangement according to the prior art, which comprises a switch plate S provided with printed circuitry. The stepping contacts 1 occupy approximately 180, the remaining 180 being occupied by an arcuate outer contact 2. The stepping contacts are formed with extensions 3 which end in terminals 4, as is shown for two of the stepping contacts. The rotary axis of the switch is shown at 5. The printed circuitry also includes a circular inner contact 6 which is arranged about the axis 5 and is partly surrounded by the stepping contacts 1. As shown in FIGURE 2, the inner contact 6 is connectible to the individual stepping contacts 1 by way of an obliquely oriented contact bridge 7 which is part of the switch and which is rotatable about the axis 5. In practice, the contact bridge 7 is fixedly and insulatedly mounted on the shaft 5 which turns about the axis 5.

As stated above, it is desirable to maintain the switch as a whole as small as possible, which means that the switch plate S and the printed circuitry thereon should be as compact as possible. As illustrated in FIGURE 1, the inner contact 6 is a ring located between the shaft 5' and the contracts 1, 2, and this means that the distance between contact 6 from the contacts 1, 2, as well as from the shaft 5 will be very small; in practice, the distances will be even smaller than shown in the drawings which are drawn on an enlarged scale to facilitate illustration of the subject matter involved. Consequently, very little 3,175,052 Patented Mar. 23, 1965 space is available to accommodate the terminal for the inner contact ring 6; in the structure shown in FIGURE 1, the terminal 8 is arranged in the space between the contact 6 and the shaft 5'.

Experience has shown that it is exceedingly difficult, if not impossible, to obtain a reliable electrical connection with the ring 6 by means of a terminal which is located in an inaccessible place such as between the contact 6 and the shaft 5'. Moreover, no way has been found to eliminate current leakages from the terminal 8 to the shaft 5', which is usually made of metal.

It is, therefore, the primary object of the present invention to provide a stepping switch which overcomes the above disadvantages, namely, a switch in which the terminal of the inner contact need no longer be accommodated in a very small and difiicultly accessible place. With this object in view, the present invention resides mainly in a stepping switch having an oblique contact bridge cooperating with a switching plate provided with printed circuitry which includes circular inner contact means arranged about the rotary axis of the switch, a plurality of stepping contacts arranged about the inner contact means, and outer contact means which are connectible to the inner contact by the contact bridge in a plurality of positions of the switch, which switch incorporates the following improvement: (a) the inner contact means are fashioned as an open ring and have an end that extends outwardly in approximately radial direction, this end serving as a terminal of the inner contact means and as a portion of the outer contact means, and (b) the outer contact means have a part extending into the ring opening and serving as a portion of the inner contact means. The term oblique, as used throughout the instant specification and claims with respect to the orienta tion of the contact bridge, is intended to refer to such a position of the bridge that a line joining the two contacts of the bridge is inclined with respect to a radial line passing through the rotary axis of the switch.

Additional objects and advantages of the present invention will become apparent upon consideration of the following description when taken in conjunction with the accompanying drawings in which:

FIGURE 1, described above, shows a switch plate structure according to the prior art.

FIGURE 2, also mentioned above, shows an oblique contact bridge adapted for use with a switch plate accord ing to the prior art as well as with a switch plate according to the present invention.

FIGURE 3 shows one embodiment of a switch plate structure according to the present invention.

FIGURE 4 shows another embodiment of a switch plate structure according to the present invention.

FIGURE 5 shows yet another embodiment of a switch plate structure according to the present invention.

Referring now to the drawings, FIGURE 3 shows a switch plate S incorporating a plurality of stepping contacts 1a arranged about the rotary axis 5a and distributed throughout approximately The remaining 180 are occupied by an outer contact 2a which is connectible to the inner contact 6a by means of the oblique contact bridge 7 shown in FIGURE 2. According to the present invention, the contact 6a is fashioned as an open ring and has an end 9 that extends outwardly in approximately radial direction. A part 10 of this end 9 serves as a portion of the outer contact, and part 11 serves as a terminal for the inner contact 6a. On the other hand, the outer contact 2a has a part 12 which extends into the ring opening and serves as a portion of the inner contact. The contact bridge is shown schematically in five positions v, w, x, y, and z, in each of which the inner and outer contacts 6a and 2a are electrically connected to each other by the bridge. In this way, the same switching 3 effect is obtained as with the known stucture depicted in FIGURE 1, with the difference that the terminal by means of which an external lead is connectible to the inner contact 6a is no longer squeezed into a difficult and inconvenient location.

In the embodiment 01": FIGURE 4, the switch plate S is provided with stepping contacts 1b arranged about the axis 5b, the inner contact 6b having its end $1) extending outwardly. The part 1% serves as a portion of the outer contact and the part 11b as the terminal. The outer contact 2b has its part 12b extending into the ring opening and serving as a portion of the inner contact. FIGURE 4 shows four switching positions w, x, y, and z, in which the inner and outer contacts 6b and 2b are connected. The embodiment of FIGURE 4 thus differs from that of FIGURE 3 in that in the latter the end 9 of the inner contact means and the part 12 of the outer contact means are coextensive throughout a portion of their circumferential lengths, whereas in the embodiment of FIGURE 4 the circumferential length of the part 12b of the outer contact means does not exceed the circumferential length of the ring opening.

The embodiment of FIGURE 5 is similar to that of FIGURE 4, and the components of the switch S are shown by analogous reference characters. The difference is that the ring opening, the end part 100, and the part 12c have a circumferential length of but one switching step, as compared to the two-step length in FIGURE 4. Two switching positions y and z are shown.

The instant invention is not limited to single pole arrangements, in that the contact 6 can be split, thereby forming a multiple-pole switching system. Furthermore, the invention may readily be incorporated in switches having either a single or a plurality of switch plates.

It will be understood that the above description of the present invention is susceptible to various modifications, changes, and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.

What is claimed is:

l, A multiple-position rotary stepping switch, comprising, in combination: a contact bridge; means inovably mounting said contact bridge for rotation about a rotaiy axis, said bridge being oriented obliquely with respect to said rotary axis; and a switching plate cooperating with said contact bridge and provided withprinted circuitry which includes a plurality of stepping contacts arranged about said rotary axis of the switch, an inner contact also arranged about said rotary axis and partly surrounded by said stepping contacts, and an outer contact connectible to said inner contact by said contact bridge in a plurality of positions of the switch, said inner contact being configured as an open ring and having an end that extends outwardly in approximately radial direc tion, said end serving as a terminal of said inner contact and as a portion of said outer contact, and said outer contact having a part extending to the ring opening and serving as a portion of said inner contact.

2. A switch as defined in claim 1 wherein said end of said inner contact and said part of said outer contact are coextensive throughout a portion of their circumferential lengths.

3. A switch as defined in claim 1 wherein said part of said outer contact has a circumferential length not exceeding the circumferential length of said ring opening.

4. A switch as defined in claim 1 wherein said inner and outer contact means are configured such that the oblique contact bridge, in each of the multiple positions of the switch, contacts both said inner and said outer contact means.

5. A switch as defined in claim 1 wherein said stepping contacts, said inner contact and said outer contact are configured such that said oblique contact bridge in each of said plurality of positions of the switch, contacts (a) said inner contact and (b) one of said stepping contacts or said outer contact.

Hartz July 21, 1959 Strathearn July 3, 1962 

1. A MULTIPLE-POSITION ROTARY STEPPING SWITCH, COMPRISING, IN COMBINATION: A CONTACT BRIDGE; MEANS MOVABLY MOUNTING SAID CONTACT BRIDGE FOR ROTATION ABOUT A ROTARY AXIS, SAID BRIDGE BEING ORIENTED OBLIQUELY WITH RESPECT TO SAID ROTARY AXIS; AND A SWITCHING PLATE COOPERATING WITH SAID CONTACT BRIDGE AND PROVIDED WITH PRINTED CIRCUITRY WHICH INCLUDES A PLURLITY OF STEPPING CONTACTS ARRANGED ABOUT SAID ROTARY AXIS OF THE SWITCH, AN INNER CONTACT ALSO ARRANGED ABOUT SAID ROTARY AXIS AND PARTLY SURROUNDING BY SAID STEPPING CONTACTS, AND AN OUTER CONTACT CONNECTIBLE TO SAID INNER CONTACT BY SAID CONTACT BRIDGE IN A PLURALITY OF POSITIONS OF THE SWITCH, SAID INNER CONTACT BEING CONFIGURED AS AN OPEN RING AND HAVING AN END THAT EXTENDS OUTWARDLY IN APPROXIMATELY RADIAL DIRECTION, SAID END SERVING AS A TERMINAL OF SAID INNER CONTACT AND AS A PORTION OF SAID OUTER CONTACT, AND SAID OUTER CONTACT HAVING A PART EXTENDING TO THE RING OPENING AND SERVING AS A PORTION OF SAID INNER CONTACT. 